The British Library has opened up its extensive bibliographic records to the Internet, adding millions of records to Amazon.co.uk's books listings. The move will make it possible for rare and antiquarian books, including nearly two million titles published before the 1970 introduction of the ISBN, to be listed on Amazon's site for the first time.

The library's bibliographic records -- information such as publisher, publication date, type of binding and number of pages -- have been added to Amazon.co.uk's catalogue as of Monday, the company said. In some cases, the information will be added to existing book listings, but it will make its most noticeable impact on Amazon's ability to list out-of-print, pre-ISBN and rare books, making rare books far easier to find online. The ISBN is an identifying number introduced by the publishing industry in 1970.

An Amazon service introduced last year called Marketplace allows third-party sellers, such as antiquarian bookshops, to list their wares directly through Amazon's main book listings. For example, the entry for "Harry Potter and the Chamber of Secrets" list's Amazon's own selling price (£4.79), but also 27 third parties selling new copies of the book (starting at £2.29), 59 used (starting at 50 pence) and eight collectible editions (starting at £20).

However, a book can only be sold through Amazon's site if a catalogue entry for it already exists, and the addition of the British Library's book data means that Amazon's catalogue has been greatly expanded. It includes relatively recent volumes such as a 1967 edition of Ivor Herbert's The Queen Mother's Horses, as well as more obscure works such as Phillippe de Monte's second book of madrigals and other titles dating back to 1570.

The library said that 1.7 million of the 2.55 million records contributed to Amazon date from before 1970.

It is also possible for booksellers to list their wares through Amazon's "zShops", which do not depend on Amazon's catalogue. But these are separate from the main product listings and are not listed in any standardised way.

When Amazon started its UK service, it listed only the 1.5 million books in print. With the introduction of Marketplace last year, the catalogue was increased to include out-of-print titles, but it was only possible to list books after 1970, according to an Amazon spokeswoman. "We have now dramatically expanded that," the spokeswoman said. "Before now, you could only get those titles from a specialist or antiquarian bookseller."

"Our bibliographic catalogues are second-to-none and we are delighted that Amazon.co.uk will be using them to underpin and support the marketplace service," said Natalie Ceeney, Director of Operations and Services at the British Library, in a statement.

The library has recently undertaken other ambitious online projects. Earlier this month it announced Collect Britain, a £3.25m digitisation project to put 100,000 unique and rare items from its collections on the Web, including illuminated manuscripts and penny illustrated newspapers.

The project also includes audio elements, such as wildlife recordings from the UK, regional dialects and ethnographic recordings from Africa and Asia.

In October, legal changes allowed the library to add archives of Web sites and emails to its legal deposit of printed materials. The electronic collection will build on a a voluntary scheme that has been in place since 2000, and will include selected pages from the 2.9 million ".uk" Web sites. The library is one of six sites that hold a copy of everything published in the UK since 1911.

MPs supporting the law hailed the decision as ensuring that an important part of the nation's published heritage would remain safe and accessible to future researchers.

Amazon recently introduced a system allowing users to browse and search the interiors of books sold on its site, a tool which industry observers said could herald big changes in the way books are published and consumed.